My pawn shop find (nickel 4" 586) came back from the factory after I sent it off for a rear sight blade replacement and requested check-up. I am pleased with my customer service experience with Smith & Wesson, and, come to find out, they apparently replaced a few internal parts. Among the parts replaced were the mainspring, cylinder stop, hand, and the rebound slide (I believe). I am not an armorer, just did some investigation to figure out which parts these were. It doesn't appear to me that there is excessive wear to these parts that were apparently replaced, but again, I'm not an armorer. My question is, is this possibly something that the factory does as a service (replaces these parts) when an older (I believe 1989 model) revolver ends up at the performance center? Just a question; I am in no way dissatisfied.